The recent guidelines recommend TKI discontinuation in CML-CP patients pre-treated for at least 3 years who exhibited molecular response with BCR-ABL1 level of < 0.01% or a 4-log reduction in transcription level respect to the baseline (MR4) for at a minimum 2 years (11). This evidence concerns the gene ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive.